Voltage generation circuit and semiconductor memory device including the same

ABSTRACT

A voltage generation circuit and semiconductor memory device including the same are provided. The voltage generation circuit includes: a voltage level detector, which detects a level of a first high voltage to generate a first high voltage level detection signal and detects a level of a second high voltage to generate a second high voltage level detection signal; a control signal generator, which generates at least four pumping control signals in sequence when the first high voltage level detection signal is active, generates a control signal when the first high voltage level detection signal is inactive, and generates a first one of the at least four pumping control signals in response to a level of a power supply voltage; and a voltage generator, which pumps a boost node in response to the at least four pumping control signals to generate the first high voltage and transmits charge from the boost node to a second high voltage generation terminal in response to the control signal to generate the second high voltage.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional application of co-pending U.S. application Ser. No.11/293,890, filed Dec. 2, 2005, which claims foreign priority under 35U.S.C. § 119 to Korean Patent Application No. 2004-101925 filed Dec. 6,2004 which is hereby incorporated by reference for all purposes as iffully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor memory device and, moreparticularly, to a voltage generation circuit, which can generatevoltages of two levels that are higher than a power supply voltage, anda semiconductor memory device including the same.

2. Description of the Related Art

A conventional semiconductor memory device makes use of a voltage levelhigher than a power supply voltage to drive a word line and makes use ofa precharge voltage equal to or half of the power supply voltage toprecharge a bit line. For this reason, the semiconductor memory deviceincludes a high voltage generator to generate the high voltage and aprecharge voltage generator to generate the precharge voltage.

The inclusion of both these voltage generators is because the powersupply voltage of the conventional semiconductor memory device is high.As the voltage level of the power supply of the semiconductor memorydevice is reduced to 1.2 V or less, the precharge voltage forprecharging the bit line should be lower than the voltage applied to theword line and higher than the power supply voltage. Accordingly, aprecharge voltage that is different from that of the conventionalsemiconductor memory device from the precharge voltage is needed.

When the precharge voltage is equal to or half of the power supplyvoltage, the precharge voltage generator is configured without acapacitor. However, when the precharge voltage is higher than the powersupply voltage, the precharge voltage generator typically includes acapacitor to pump the power supply voltage.

Therefore, a semiconductor memory device using a low power supplyvoltage has an increased layout area compared to a semiconductor memorydevice using a high power supply voltage, because both a high voltagegenerator and a precharge voltage generator include capacitors.

SUMMARY OF THE INVENTION

One embodiment of the invention provides a voltage generation circuit,which generates two different levels of boost voltage that are higherthan a power supply voltage by sharing a capacitor, thereby integratinginto a small layout area.

Another embodiment of the invention provides a semiconductor memorydevice including the above-described voltage generation circuit.

In one aspect of the present invention, a voltage generation circuitincludes a voltage level detector, which detects a level of a first highvoltage to generate a first high voltage level detection signal anddetects a level of a second high voltage to generate a second highvoltage level detection signal; a control signal generator, whichgenerates at least three pumping control signals in sequence in responseto the first high voltage level detection signal and generates at leastone of the at least three pumping control signals in response to thesecond high voltage level detection signal, and a voltage generator,which pumps a boost node in response to the at least three pumpingcontrol signals to generate the first high voltage and pumps the boostnode in response to the at least one of the at least three pumpingcontrol signals to generate the second high voltage.

When the first and second high voltage level detection signals areactive at about the same time, the control signal generator mayalternately perform an operation of generating a first one, a secondone, and a third one of the at least three pumping control signals insequence and an operation of generating the at least one of the at leastthree pumping control signals. The control signal generator may includea detection signal generator, which generates a first detection signalwhen the first high voltage level detection signal is active, generatesa second detection signal when the second high voltage level detectionsignal is active, and generates a third detection signal when the firstand second high voltage level detection signals are active at about thesame time, an oscillation signal generator, which generates a firstoscillation signal in response to the first high voltage level detectionsignal or the second high voltage level detection signal and generates asecond oscillation signal by dividing the first oscillation signal, afirst high voltage pumping control signal generator, which generates afirst signal from the second oscillation signal when the third detectionsignal is generated and generates a first high voltage pumping controlsignal from the first oscillation signal in response to the first highvoltage level detection signal or the first signal, and a second highvoltage pumping control signal generator, which generates a secondsignal from an inverted second oscillation signal when the thirddetection signal is generated and generates a second high voltagepumping control signal from the first oscillation signal in response tothe second high voltage level detection signal or the second signal,wherein the control signal generator generates the at least threepumping control signals in response to the first high voltage pumpingcontrol signal and generates the at least one of the at least threepumping control signals in response to the second high voltage pumpingcontrol signal. The control signal generator may generate a firstprecharge control signal in response to the first one of the at leastthree pumping control signals, a second precharge control signal inresponse to the first one and the second one of the at least threepumping control signals, and a third precharge control signal inresponse to the first one, the second one, and the third one of the atleast three pumping control signals.

In one embodiment, the voltage generator may include a first and secondpumping and precharge unit, which pumps a first node and a second nodein response to the first one of the at least three pumping controlsignals and performs charge sharing operations between the first nodeand the boost node and between the second node and a third node duringthe generation of the first high voltage, and precharges the first andsecond nodes in response to the first precharge control signal, a thirdpumping and precharge unit, which pumps the third node in response tothe second one of the at least three pumping control signals andperforms a charge sharing operation between the third node and the boostnode during the generation of the first high voltage, and precharges thethird node in response to the second precharge control signal, and afourth pumping and precharge unit, which pumps the boost node inresponse to the third one of the at least three pumping control signalsand performs a charge sharing operation between the boost node and afirst high voltage generation terminal during the generation of thefirst high voltage, pumps the boost node in response to the third one ofthe at least three pumping control signals and performs a charge sharingoperation between the boost node and a second high voltage generationterminal during the generation of the second high voltage, andprecharges the boost node in response to the third precharge controlsignal. In another embodiment, the voltage generator may include a firstand second pumping and precharge unit, which pumps a first node and asecond node in response to the first one of the at least three pumpingcontrol signals and performs charge sharing operations between the firstnode and the boost node and between the second node and a third nodeduring the generation of the first high voltage, and precharges thefirst and second nodes, a third pumping and precharge unit, which pumpsthe third node in response to the second one of the at least threepumping control signals and performs a charge sharing operation betweenthe third node and the boost node during the generation of the first andsecond high voltages, and precharges the third node, and a fourthpumping and precharge unit, which pumps the boost node in response tothe third one of the at least three pumping control signals and performsa charge sharing operation between the boost node and a first highvoltage generation terminal during the generation of the first highvoltage, pumps the boost node in response to the third one of the atleast three pumping control signals and performs a charge sharingoperation between the boost node and a second high voltage generationterminal during the generation of the second high voltage, andprecharges the boost node.

In a second aspect of the present invention, a voltage generationcircuit includes a voltage level detector, which detects a level of afirst high voltage to generate a first high voltage level detectionsignal and detects a level of a second high voltage to generate a secondhigh voltage level detection signal, a control signal generator, whichgenerates at least four pumping control signals in sequence when thefirst high voltage level detection signal is active and generates acontrol signal when the first high voltage level detection signal isinactive, and a voltage generator, which pumps a boost node in responseto the at least four pumping control signals to generate the first highvoltage and transmits charge from the boost node to a second highvoltage generation terminal in response to the control signal togenerate the second high voltage.

The control signal generator may activate a first one, a second one, anda third one of the at least four pumping control signals, which areactivated in sequence during the active period of the first high voltagelevel detection signal, activate a fourth one of the at least fourpumping control signals, which is activated during the inactive periodof the first high voltage level detection signal, and generate a firstprecharge control signal in response to the first one of the at leastfour pumping control signals, a second precharge control signal inresponse to the first one and the second one of the at least fourpumping control signals, and a third precharge control signal inresponse to the first one of the at least four pumping control signalsand the control signal.

In a third aspect of the present invention, a voltage generation circuitincludes a voltage level detector, which detects a level of a first highvoltage to generate a first high voltage level detection signal anddetects a level of a second high voltage to generate a second highvoltage level detection signal, a control signal generator, whichgenerates at least four pumping control signals in sequence when thefirst high voltage level detection signal is active, generates a controlsignal when the first high voltage level detection signal is inactive,and generates a first one of the at least four pumping control signalsin response to a level of a power supply voltage, and a voltagegenerator, which pumps a boost node in response to the at least fourpumping control signals to generate the first high voltage and transmitscharge from the boost node to a second high voltage generation terminalin response to the control signal to generate the second high voltage.

The control signal generator may include a power supply voltage leveldetector, which generates the first one of the at least four pumpingcontrol signals in response to the level of the power supply voltage,receives the first one of the at least four pumping control signals andoutputs an output signal when the power supply voltage is at apredetermined level or higher, and deactivates the first one of the atleast four pumping control signals when the power supply voltage is at alevel lower than the predetermined level.

The control signal generator may activate the first one, a second one,and a third one of the at least foul pumping control signals, which areactivated in sequence during the active period of the first high voltagelevel detection signal, activate a fourth one of the at least fourpumping control signals, which is activated during the inactive periodof the first high voltage level detection signal, generate a firstprecharge control signal in response to the first one of the at leastfour pumping control signals, a second precharge control signal inresponse to the first one and the second one of the at least fourpumping control signals, and a third precharge control signal inresponse to the first one of the at least four pumping control signalsand the control signal, activate the first one of the at least fourpumping control signals when the power supply voltage is at a highlevel, and deactivate the first one of the at least four pumping controlsignals when the power supply voltage is at a low level.

In the second and third aspects of the present invention, the voltagegenerator may include a first high voltage generator, which pumps theboost node in response to the at least four pumping control signals togenerate the first high voltage, and a second high voltage generator,which transmits charge from the boost node to the second high voltagegeneration terminal in response to the control signal and the secondhigh voltage level detection signal to generate the second high voltage.The first high voltage generator may include a first and second pumpingand precharge unit, which pumps a first node and a second node inresponse to the first one of the at least four pumping control signalsand performs charge sharing operations between the first node and theboost node and between the second node and a third node during thegeneration of the first high voltage, and precharges the first andsecond nodes in response to the first precharge control signal, a thirdpumping and precharge unit, which pumps the third node in response tothe second one of the at least four pumping control signals and performsa charge sharing operation between the third node and the boost nodeduring the generation of the first and second high voltages andprecharges the third node in response to the second precharge controlsignal, and a fourth pumping and precharge unit, which pumps the boostnode in response to the third one of the at least four pumping controlsignals and performs a charge sharing operation between the boost nodeand a first high voltage generation terminal during the generation ofthe first high voltage, pumps the boost node in response to the thirdone of the at least four pumping control signals and performs a chargesharing operation between the boost node and a second high voltagegeneration terminal during the generation of the second high voltage,and precharges the boost node in response to the third precharge controlsignal. The second high voltage generator may include a second highvoltage generation unit, which transmits charge from the boost node tothe second high voltage generation terminal in response to the controlsignal and the second high voltage level detection signal.

The first and second pumping and precharge unit may include a firstswitch, which is connected between the power supply voltage and thefirst node and precharges the first node in response to the firstprecharge control signal, a first capacitor, which pumps the first nodein response to the first one of the at least four pumping controlsignals, a second switch, which is connected between the power supplyvoltage and the second node and precharges the second node in responseto the first precharge control signal, a second capacitor, which pumpsthe second node in response to the first one of the at least fourpumping control signals; a third switch, which is turned on in responseto the first one of the at least four pumping control signals and allowscharge to be shared by the first node and the boost node, and a fourthswitch, which is turned on in response to the first one of the at leastfour pumping control signals and allows charge to be shared by thesecond node and the third node. The third pumping and precharge unit mayinclude a fifth switch, which is connected between the power supplyvoltage and the third node and is turned on in response to the secondprecharge control signal to precharge the third node, a third capacitor,which pumps the third node in response to the second one of the at leastfour pumping control signals, and a sixth switch, which is turned on inresponse to the second one of the at least four pumping control signalsand allows charge to be shared by the third node and the boost node.Also, the fourth pumping and precharge unit may include: a seventhswitch, which is connected between the power supply voltage and theboost node and precharges the boost node in response to the thirdprecharge control signal, a fourth capacitor, which pumps the boost nodein response to the third one of the at least four pumping controlsignals, and an eighth switch, which allows charge to be shared by theboost node and the first high voltage generation terminal in response tothe third one of the at least four pumping control signals during thegeneration of the first high voltage. The second high voltage generationunit may include a ninth switch, which transmits charge from the boostnode in response to the control signal, and a tenth switch, whichtransmits charge transmitted from the ninth switch to the second highvoltage generation terminal in response to the second high voltage leveldetection signal. The second high voltage generation unit may furtherinclude an eleventh switch, which transmits charge transmitted to thesecond high voltage generation terminal to a power supply voltagegeneration terminal when the second high voltage level detection signalis inactive.

In a fourth aspect of the present invention, a semiconductor memorydevice includes a voltage generation circuit including a voltage leveldetector, which detects a level of a high voltage to generate a highvoltage level detection signal and detects a level of a prechargevoltage to generate a precharge voltage level detection signal, acontrol signal detector, which generates at least foul pumping controlsignals in sequence when the high voltage level detection signal isactive and generates a control signal when the high voltage leveldetection signal is inactive, and a voltage generator, which pumps aboost node in response to the at least four pumping control signals togenerate the high voltage and transmits charge from the boost node to aprecharge voltage generation terminal in response to the control signalto generate a precharge voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the invention will be apparent fromthe following detailed description of preferred embodiments, asillustrated in the accompanying drawings.

FIG. 1 is a block diagram of a voltage generation circuit according toan exemplary embodiment of the present invention.

FIG. 2 is a block diagram of a controller shown in FIG. 1.

FIGS. 3A through 3C are timing diagrams illustrating operations of thevoltage generation circuit and controller shown in FIGS. 1 and 2.

FIG. 4 is a block diagram of a voltage generation circuit according toanother exemplary embodiment of the present invention.

FIG. 5 is a timing diagram illustrating operations of the voltagegeneration circuit shown in FIG. 4.

FIG. 6 is a block diagram of a voltage generation circuit according toyet another exemplary embodiment of the present invention.

FIGS. 7A and 78B are timing diagrams illustrating operations of thevoltage generation circuit shown in FIG. 6.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A voltage generation circuit and semiconductor memory device includingthe same according to the present invention will now be described morefully hereinafter with reference to the accompanying drawings.

FIG. 1 is a block diagram of a voltage generation circuit according toan exemplary embodiment of the present invention. Referring to FIG. 1,the voltage generation circuit includes a precharge voltage leveldetector 10, a high voltage level detector 12, a controller 14, and ahigh voltage and precharge voltage generator 16. The high voltage andprecharge voltage generator 16 includes first through fourth capacitorsC1-C4 and first through ninth switches SW1-SW9.

The precharge voltage level detector 10 receives a precharge voltage Veqand generates a precharge voltage level detection signal VEQEN when theprecharge voltage Veq is at a level equal to or lower than a targetlevel. The high voltage level detector 12 receives a high voltage Vppand generates a high voltage level detection signal VPPEN when the highvoltage Vpp is at a level equal to or lower than a target level. Thecontroller 14 generates first through third pumping control signalsP1-P3 and first through third precharge control signals PP1-PP3 inresponse to the precharge voltage level detection signal VEQEN and thehigh voltage level detection signal VPPEN. When the precharge voltagelevel detection signal VEQEN and the high voltage level detection signalVPPEN are active at the same time, the controller 14 alternatelyperforms an operation of generating the first through third pumpingcontrol signals P1-P3 and the first through third precharge controlsignals PP1-PP3 in response to the high voltage level detection signalVPPEN and an operation of generating the third pumping control signal P3and the third precharge control signal PP3 in response to the prechargevoltage level detection signal VEQEN. The high voltage and prechargevoltage generator 16 pumps a boost node n4 three times in response tothe first through third pumping control signals P1-P3 and generates thehigh voltage Vpp. Also, the high voltage and precharge voltage generator16 pumps the boost node n4 once in response to the third pumping controlsignal P3 and generates the precharge voltage Veq. The first, second,third and sixth switches SW1, SW2, SW3, and SW6 precharge first, secondand third nodes n1, n2 and n3 and the boost node n4 to about the levelof a power supply voltage Vdd, respectively in response to the first,second and third precharge control signals PP1, PP2, and PP3, which areat high logic levels. The first aid second capacitors C1 and C2 pump thefirst and second nodes n1 and n2, respectively, in response to the firstpumping control signal P1 which is at a high logic level. The thirdcapacitor C3 pumps the third node n3 in response to the second pumpingcontrol signal P2 that is at a high logic level, and the fourthcapacitor C4 pumps the boost node n4 in response to the third pumpingcontrol signal P3 that is at a high logic level. The fourth and fifthswitches SW4 and SW5 are turned on in response to the first pumpingcontrol signal P1 that is at a high logic level, the seventh switch SW7is turned on in response to the second pumping control signal P2 that isat a high logic level, and the eighth switch SW8 is turned on inresponse to the third pumping control signal P3 and the high voltagelevel detection signal VPPEN that are at high logic levels. Also, theninth switch SW9 is turned on in response to the third pumping controlsignal P3 and the precharge voltage level detection signal VEQEN thatare at high logic levels.

The high voltage and precharge voltage generator 16 makes use of thefirst through fourth capacitors C1-C4 to generate the high voltage Vppand makes use of the fourth capacitor C4 to generate the prechargevoltage Veq. Since the high voltage and precharge voltage generator 16needs no additional capacitors to generate the precharge voltage Veq, ithas a small layout area.

FIG. 2 is a block diagram of the controller shown in FIG. 1. Referringto FIG. 2, the controller 14 includes first, second and third detectioncircuits 20, 22, and 24, a pulse generator 26, a high voltage pumpingcontrol signal generator 28, a precharge voltage pumping control signalgenerator 30, and a control signal generator 32.

The first detection circuit 20 includes first and second inverters I1and I2 and a first NAND gate NA1, and the second detection circuit 22includes a second NAND gate NA2 and a third inverter I3. The thirddetection circuit 24 includes sixth and seventh inverters I6 and I7 anda seventh NAND gate NA7, and the pulse generator 26 includes a first NORgate NOR1, a fifth inverter I5, an oscillator 26-1, and a divider 26-2.Also, the high voltage pumping control signal generator 28 includesthird through sixth NAND gates NA3-NA6 and a fourth inverter I4, and theprecharge voltage pumping control signal generator 30 includes eighththrough eleventh NAND gates NA8-NA11 and eighth and ninth inverters I8and I9.

The first detection circuit 20 generates a first signal a when only thehigh voltage level detection signal VPPEN is active. The seconddetection circuit 22 generates a second signal b when both the highvoltage level detection signal VPPEN and the precharge voltage leveldetection signal VEQEN are active. The third detection circuit 24generates a fourth signal d when only the precharge voltage leveldetection signal VEQEN is active. The pulse generator 26 generates asixth signal f when at least one of the high voltage level detectionsignal VPPEN or the precharge voltage level detection signal VEQEN areactive, generates a first oscillation signal OSC1 that oscillates at apredetermined frequency in response to the sixth signal f, and generatesa second oscillation signal OSC2 by dividing the first oscillationsignal OSC1. That is, the oscillator 26-1 generates the firstoscillation signal OSC1 that oscillates in response to the sixth signalf, and the divider 26-2 divides the first oscillation signal OSC1 togenerate the second oscillation signal OSC2. The high voltage pumpingcontrol signal generator 28 generates the second oscillation signal OSC2as a third signal c when the second signal b is active and generates thefirst oscillation signal OSC1 as a high voltage pumping control signalVPEN when the third signal c or the first signal a are active. Theprecharge voltage pumping control signal generator 30 generates aninverted second oscillation signal OSC2 as a fifth signal e when thesecond signal b is active and the first oscillation signal OSC1 as aprecharge voltage pumping control signal VEEN when the fourth signals dor the fifth signal e are active. The control signal generator 32generates the first, second and third pumping control signals P1, P2,and P3, which are activated in sequence while the high voltage pumpingcontrol signal VPEN is active, and generates the first, second and thirdprecharge control signals PP1, PP2, and PP3 corresponding to the first,second and third pumping control signals P1, P2, and P3, respectively.

FIGS. 3A through 3C are timing diagrams illustrating operations of thevoltage generation circuit and controller shown in FIGS. 1 and 2.Specifically, FIG. 3A illustrates the operation of the voltagegeneration circuit when both the high voltage level detection signalVPPEN and the precharge voltage level detection signal VEQEN are at highlogic levels, FIG. 3B illustrates the operation of the voltagegeneration circuit when the high voltage level detection signal VPPEN isat a high logic level and the precharge voltage level detection signalVEQEN is at a low logic level, and FIG. 3C illustrates the operation ofthe voltage generation circuit when the precharge voltage leveldetection signal VEQEN is at a high logic level and the high voltagelevel detection signal VPPEN is at a low logic level.

Referring to FIG. 3A, when both the high voltage level detection signalVPPEN and the precharge voltage level detection signal VEQEN are at highlogic levels, the sixth signal f of FIG. 2 gets to a high logic level.Thus, the oscillator 26-1 and the divider 26-2 perform their respectiveoperations to generate the first and second oscillation signals OSC1 andOSC2. Also, the first and third detection circuits 20 and 24 generatethe first and fourth signals a and d that are at low logic levels, andthe second detection circuit 22 generates the second signal b that is ata high logic level. The high voltage pumping control signal generator 28generates the second oscillation signal OSC2 as the third signal c inresponse to the second signal b that is at a high logic level andgenerates the first oscillation signal OSC1 as the high voltage pumpingcontrol signal VPEN in response to the third signal c. The prechargevoltage pumping control signal generator 30 generates the invertedsecond oscillation signal OSC2 as the fifth signal e in response to thesecond signal b that is at a high logic level and generates the firstoscillation signal OSC1 as the precharge voltage pumping control signalVEEN in response to the fifth signal e. The control signal generator 32alternately performs an operation of generating the first, second andthird pumping control signals P1, P2, and P3 in sequence in response tothe high voltage pumping control signal VPEN and an operation ofgenerating the third pumping control signal P3 in response to theprecharge voltage pumping control signal VEEN. Also, the control signalgenerator 32 generates the first precharge control signal PP1, which isan inverted first pumping control signal P1, generates the secondprecharge control signal PP2, which is inactive when the first pumpingcontrol signal P1 is active and active when the second pumping controlsignal P2 is inactive, and generates the third precharge control signalPP3, which is inactive when the first pumping control signal P1 isactive and active when the third pumping control signal P3 is inactive.

In the high voltage and precharge voltage generator 16, when the first,second and third pumping control signals P1, P2, and P3 are activated insequence, the first, second, third and sixth switches SW1, SW2, SW3, andSW6 are turned on in response to the first through third prechargecontrol signals PP1-PP3 that are at high logic levels, so that thefirst, second, third and boost nodes n1, n2, n3 and n4 are precharged toabout the level of the power supply voltage Vdd. In this state, once thefirst, second and third precharge control signals PP1, PP2, and PP3 getto a low logic level and the first pumping control signal P1 gets to ahigh logic level, the first and second switches SW1 and SW2 are turnedoff and the first and second capacitors C1 and C2 allow the first andsecond nodes n1 and n2 to be pumped to about 2Vdd. After that, thefourth and fifth switches SW4 and SW5 are turned on, and the first andboost nodes n1 and n4 share charge and the second and third nodes n2 andn3 also share charge so that the first, second, third and boost nodesn1, n2, n3 and n4 are charged to about 1.5Vdd. Thereafter, once thefirst precharge control signal PP1 gets to a high logic level and thesecond pumping control signal P2 gets to a high logic level, the firstand second switches SW1 and SW2 are turned on, so that the first andsecond nodes n1 and n2 are precharged to about Vdd and the thirdcapacitor C3 allows the third node n3 to be pumped to about 2.5Vdd.After that, the seventh switch SW7 is turned on, and thus the third andboost nodes n3 and n4 share charge so that both the third and boostnodes n3 and n4 are charged to about 2Vdd. Thereafter, once the secondprecharge control signal PP2 gets to a high logic level and the thirdpumping control signal P3 gets to a high logic level, the third switchSW3 is turned on so that the third node n3 is precharged to about Vddand the fourth capacitor C4 allows the boost node n4 to be pumped toabout 3Vdd. Thereafter, the eighth switch SW8 is turned on, and chargeis shared by the boost node n4 and a high voltage generation terminal sothat both the boost node n4 and the high voltage generation terminal arecharged to about (3Vdd+Vpp)/2. Also, once the third precharge controlsignal PP3 gets to a high logic level, the sixth switch SW6 is turned onso that the boost node n4 is precharged to about Vdd. In this manner,the high voltage and precharge voltage generator 16 performs a highvoltage pumping operation.

In the high voltage and precharge voltage generator 16, when the firstpumping control signal P1 is not active and the second and third pumpingcontrol signals P2 and P3 are activated in sequence, the first, second,third and sixth switches SW1, SW2, SW3, and SW6 are turned on inresponse to the first through third precharge control signals PP1-PP3that are at high logic levels, so that the first, second, third andboost nodes n1, n2, n3 and n4 are precharged to about Vdd. In thisstate, once the third pumping control signal P3 gets to a high logiclevel, the fourth capacitor C4 allows the boost node n4 to be pumped toabout 2Vdd. After that, the ninth switch SW9 is turned on, and charge isshared by the boost node n4 and a precharge voltage generation terminalso that both the boost node n4 and the precharge voltage generationterminal are charged to about (2Vdd+Veq)/2. Thereafter, once the thirdprecharge control signal PP3 gets to a high logic level, the boost noden4 is precharged to about Vdd. In this manner, the high voltage andprecharge voltage generator 16 performs a precharge voltage pumpingoperation.

Referring to FIG. 3B, when the high voltage level detection signal VPPENis active at a high logic level and the precharge voltage leveldetection signal VEQEN is inactive at a low logic level, only the highvoltage pumping control signal VPEN is active continuously, so that thefirst, second and third pumping control signals P1, P2, and P3 areactivated in sequence. Accordingly, the high voltage and prechargevoltage generator 16 keeps performing the same high voltage pumpingoperation as described with reference to FIG. 3A.

Referring to FIG. 3C, when the high voltage level detection signal VPPENis inactive at a low logic level and the precharge voltage leveldetection signal VEQEN is active at a high logic level, only theprecharge voltage pumping control signal VEEN is active continuously, sothat only the third pumping control signal P3 is activated. Accordingly,the high voltage and precharge voltage generator 16 keeps performing thesame precharge voltage pumping operation as described with reference toFIG. 3A.

In the present embodiment the voltage generation circuit generates theprecharge voltage Veq by performing a pumping operation using only thethird pumping control signal P3. However, when it is necessary to boostthe precharge voltage Veq to a higher level, the voltage generationcircuit may generate the precharge voltage Veq by performing a pumpingoperation using the second and third pumping control signals P2 and P3.In this case, the control signal generator 32 may be adjusted togenerate the second and third pumping control signals P2 and P3 that areactivated in sequence in response to the precharge voltage pumpingcontrol signal VEEN.

FIG. 4 is a block diagram of a voltage generation circuit according toanother exemplary embodiment of the present invention. In the presentembodiment, the voltage generation circuit includes a precharge voltagelevel detector 40, a high voltage level detector 42, a control signalgenerator 44, and a high voltage and precharge voltage generator 46. Thehigh voltage and precharge voltage generator 46 includes capacitors C1-C4 and switches SW1-SW10, and the switch SW10 includes CMOStransmission gates T1 and T2 and an inverter I10.

The functions of the precharge voltage level detector 40 and the highvoltage level detector 42 are the same as those of the precharge voltagelevel detector 10 and the high voltage level detector 12 shown inFIG. 1. The control signal generator 44 generates first, second andthird pumping control signals P1, P2, and P3 in sequence when a highvoltage level detection signal VPPEN is active and generates a fourthpumping control signal P4 when the high voltage level detection signalVPPEN is inactive. That is, the control signal generator 44 generatesthe first through fourth pumping control signals P1-P4 in response tothe high voltage level detection signal VPPEN irrespective of whether aprecharge voltage level detection signal VEQEN is active or not. Thefunctions of the capacitors C1-C4 and the switches SW1-SW8 are the sameas those of the capacitors C1-C4 and the switches SW1-SW8 shown inFIG. 1. The switch SW9 is turned on in response to the fourth pumpingcontrol signal P4. The switch SW10 transmits charge to a power supplyvoltage generation terminal in response to the precharge voltage leveldetection signal VEQEN that is at a low logic level and transmits chargeto a precharge voltage generation terminal in response to the prechargevoltage level detection signal VEQEN that is at a high logic level. TheCMOS transmission gate T1 is turned on in response to the prechargevoltage level detection signal VEQEN that is at a high logic level, thuselevating the voltage level of the precharge voltage Veq. Also, the CMOStransmission gate T1 is turned on in response to the precharge voltagelevel detection signal VEQEN that is at a low logic level, thuselevating the voltage level of the power supply voltage Vdd.

In other words, the voltage generation circuit shown in FIG. 4 does notdirectly precharge a voltage of a boost node n4, which is pumped by thehigh voltage and precharge voltage generator 46, but makes use of thevoltage of the boost node n4 to elevate the voltage level of theprecharge voltage Veq.

Accordingly, since the voltage generation circuit shown in FIG. 4requires no additional capacitor for pumping operations to generate theprecharge voltage, it can be integrated with a small layout area.

FIG. 5 is a timing diagram illustrating operations of the voltagegeneration circuit shown in FIG. 4. The operations of the voltagegeneration circuit shown in FIG. 4 will be described below withreference to FIG. 5.

When the high voltage level detection signal VPPEN is at a high logiclevel, the first, second and third pumping control signals P1, P2, andP3 are activated in sequence. Since an operation of generating the highvoltage Vpp by elevating the voltage levels of the first, second, thirdand boost nodes n1, n2, n3 and n4 in response to the first, second andthird pumping control signals P1, P2, and P3 is the same as describedwith reference to FIG. 3A, a description thereof will be omitted here.

After the high voltage Vpp is generated, the boost node n4 is charged toabout (3Vdd+Vpp)/2. Then, when the high voltage level detection signalVPPEN is inactive at a low logic level, the control signal P4 isactivated. Once the control signal P4 is active, the switch SW9 isturned on so that charge is transmitted from the boost node n4 to afifth node n5. In this case, if the precharge voltage level detectionsignal VEQEN is at a high logic level, the CMOS transmission gate T1 isturned on, and thus the charge transmitted to the fifth node n5 istransmitted to the precharge voltage generation terminal to elevate theprecharge voltage Veq. If the precharge voltage level detection signalVEQEN is at a low logic level, the CMOS transmission gate T2 is turnedon, and the charge transmitted to the fifth node n5 is transmitted tothe power supply voltage generation terminal to elevate the power supplyvoltage Vdd. Thereafter, once the third precharge control signal PP3 isactive, the switch SW6 is turned on so that the boost node n4 isprecharged to about Vdd.

When the high voltage level detection signal VPPEN is active, thevoltage generation circuit shown in FIG. 4 generates the high voltageVpp. When the high voltage level detection signal VPPEN is inactive andthe precharge voltage level detection signal VEQEN is active, thevoltage generation circuit shown in FIG. 4 transmits charge from theboost node n4, which is produced during the generation of the highvoltage Vpp, to the precharge voltage generation terminal and thenprecharges the charge of the boost node n4. In other words, the voltagegeneration circuit shown in FIG. 4 reuses the charge from the boost noden4, which is produced during the generation of the high voltage Vpp, toelevate the level of the precharge voltage Veq.

FIG. 6 is a block diagram of a voltage generation circuit according toyet another exemplary embodiment of the present invention. In thepresent embodiment, the voltage generation circuit includes a prechargevoltage level detector 60, a high voltage level detector 62, acontroller 64, and a high voltage and precharge voltage generator 66.Also, the controller 64 includes a control signal generator 64-1, apower supply voltage level detector 64-2, a NAND gate NA12, and aninverter I11. The high voltage and precharge voltage generator 66 isstructurally the same as the high voltage and precharge voltagegenerator 46 shown in FIG. 4.

Since the operations of the precharge voltage level detector 60 and thehigh voltage level detector 62 are the same as those of the prechargevoltage level detector 10 and the high voltage level detector 12 shownin FIG. 1, a description thereof will be omitted here. Also, since theoperations of the high voltage and precharge voltage generator 66 andthe control signal generator 64-1 are the same as those of the highvoltage and precharge voltage generator 46 and the control signalgenerator 44 shown in FIG. 4, a description thereof will be omitted.Accordingly, only the functions of additional blocks will be describedhere.

The power supply voltage level detector 64-2 detects whether a powersupply voltage Vdd is at a high level or low level and generates a powersupply voltage level detection signal DET. For example, when the powersupply voltage Vdd is lower than half of the high voltage (Vpp/2), it isat a low logic level, and when the power supply voltage Vdd is equal toor higher than the half of the high voltage (Vpp/2), it is at a highlogic level. When the power supply voltage level detector 64-2 detects alow power supply voltage, it generates a power supply voltage leveldetection signal DET that is at a low logic level. Also, when the powersupply voltage level detector 64-2 detects a high power supply voltage,it generates a power supply voltage level detection signal DET that isat a high logic level. The NAND gate NA12 and the inverter I11 generatea control signal P10 that is at a high logic level when both the firstpumping control signal P1 and the power supply voltage level detectionsignal DET are at high logic levels. However, when the first pumpingcontrol signal P1 is at a high logic level and the power supply voltagelevel detection signal DET is at a low logic level, the NAND gate NA12and the inverter I11 generate the control signal P10 that is at a lowlogic level. That is, the NAND gate NA12 and the inverter I11 activatethe control signal P10 during the active period of the first pumpingcontrol signal P1 when the power supply voltage Vdd is at a high leveland deactivate the control signal P10 even during the active period ofthe first pumping control signal P1 when the power supply voltage Vdd isat a low level.

When the control signal P10 is activated, the high voltage and prechargevoltage generator 66 performs the same operation as the high voltage andprecharge voltage generator 46 shown in FIG. 4. When the control signalP10 is deactivated, capacitors C1 and C2 do not perform a pumpingoperation but only capacitors C3 and C4 perform a pumping operation.

The voltage generation circuit shown in FIG. 6 may generate highvoltages Vdd different from each other according to the level of thepower supply voltage Vdd and also, generate a precharge voltage Veqwithout any additional capacitor for generating the precharge voltageVeq. Accordingly, the voltage generation circuit shown in FIG. 6 can beintegrated with a small layout area.

FIGS. 7A and 7B are timing diagrams illustrating operations of thevoltage generation circuit shown in FIG. 6. Specifically, FIG. 7Aillustrates the operation of the voltage generation circuit when thepower supply voltage Vdd is at a high level, and FIG. 7B illustrates theoperation of the voltage generation circuit when the power supplyvoltage Vdd is at a low level.

Referring to FIG. 7A, when a high voltage level detection signal VPPENis activated, the control signal generator 64-1 generates the first,second and third pumping control signals P1, P2, and P3 in sequence.When the power supply voltage level detection signal DET is at a highlogic level, the first, second and third pumping control signals P1, P2,and P3 are activated in sequence. Then, the high voltage and prechargevoltage generator 66 performs the same operation as described withreference to FIG. 5 to generate the high voltage Vpp.

When the high voltage level detection signal VPPEN is inactive, thecontrol signal generator 64-1 generates a control signal P4. Then, thehigh voltage and precharge voltage generator 66 performs the sameoperation as described with reference to FIG. 5.

Referring to FIG. 7B, when the high voltage level detection signal VPPENis activated, the control signal generator 64-1 generates the first,second and third pumping control signals P1, P2, and P3 in sequence,When the power supply voltage level detection signal DET is at a lowlogic level, the first pumping control signal P1 is deactivated and thesecond and third pumping control signals P2 and P3 are activated insequence. Then, the high voltage and precharge voltage generator 66performs a pumping operation in response to the second and third pumpingcontrol signals P2 and P3 to generate the high voltage Vpp. In otherwords, when the second pumping control signal P2 is activated, thecapacitor C3 allows a node n3 to be pumped to about 2Vdd. Thereafter, aswitch SW7 is turned on, and charge is shared by the node n3 and a boostnode n4 so that the third and boost nodes n3 and n4 are charged to about1.5Vdd. When the third pumping control signal P3 is active, thecapacitor C4 allows the boost node n4 to be pumped to about 2.5Vdd.Thereafter, a switch SW8 is turned on, and charge is shared by the boostnode n4 and the high voltage generation terminal so that the boost noden4 and the high voltage generation terminal are charged to about((2.5Vdd+Vpp)/2. As a result, the capacitors C3 and C4 perform a pumpingoperation twice to generate the high voltage Vpp. Accordingly, when thepower supply voltage level detection signal DET is at a low logic level,the high voltage and precharge voltage generator 66 generates the highvoltage Vpp that is at a lower level than the high voltage Vpp generatedwhen the power supply voltage level detection signal DET is at a highlogic level.

Also, when the high voltage level detection signal VPPEN is inactive,the control signal generator 64-1 generates the control signal P4. Then,a switch SW9 is turned on so that charge is transmitted from the boostnode n4 to a fifth node n5. Also, when a precharge voltage leveldetection signal VEQEN is at a high logic level, a CMOS transmissiongate T1 is turned on to elevate the precharge voltage Veq. When theprecharge voltage level detection signal VEQEN is at a low logic level,a CMOS transmission gate T2 is turned on to elevate the power supplyvoltage Vdd. Thereafter, when the third precharge control signal PP3 isactivated, a switch SW6 is turned on so that the boost node n4 isprecharged to about Vdd.

In conclusion, the voltage generation circuit shown in FIG. 6 can sensethe level of the power supply voltage Vdd to generate two different highvoltages and can generate the precharge voltage Veq without anyadditional capacitor for generating the precharge voltage Veq.

In the above-described embodiments, switches may be comprised of MOStransistors. In this case, control signals are transmitted to gates ofthe MOS transistors.

The voltage generation circuit according to the present invention cangenerate at least two voltages, such as a high voltage and a prechargevoltage, which are different from each other and higher than a powersupply voltage. This circuit can generate the precharge voltage withoutusing additional capacitors and without increasing its layout area froma single high voltage generator circuit. Accordingly, the high voltagegeneration circuit can be integrated into semiconductor memory devicesusing a small layout area. Other embodiments can generate differentvoltages by performing multiple pumping operations.

Preferred embodiments of the present invention have been disclosedherein and, although specific terms are employed, they are used and areto be interpreted in a generic and descriptive sense only and not forpurpose of limitation. Accordingly, it will be understood by those ofordinary skill in the art that various changes in form and details maybe made without departing from the spirit and scope of the presentinvention as set forth in the following claims.

1. A voltage generation circuit comprising: a voltage level detector;which detects a level of a first high voltage to generate a first highvoltage level detection signal and detects a level of a second highvoltage to generate a second high voltage level detection signal; acontrol signal generator, which generates at least four pumping controlsignals in sequence when the first high voltage level detection signalis active and generates a control signal when the first high voltagelevel detection signal is inactive; and a voltage generator, which pumpsa boost node in response to the at least four pumping control signals togenerate the first high voltage and transmits charge from the boost nodeto a second high voltage generation terminal generating the second highvoltage in response to the control signal to generate the second highvoltage, wherein the control signal generator activates at least one ofthe at least three pumping control signals to generate the controlsignal in response to the second high voltage level detection signal. 2.The voltage generation circuit according to claim 1, wherein when thefirst and second high voltage level detection signals are active atabout the same time, the control signal generator alternately performsan operation of generating a first one, a second one, and a third one ofthe at least three pumping control signals in sequence and an operationof activating the at least one of the at least three pumping controlsignals.
 3. The voltage generation circuit according to claim 2, whereinthe control signal generator comprises: a detection signal generator,which generates a first detection signal when the first high voltagelevel detection signal is active, generates a second detection signalwhen the second high voltage level detection signal is active, andgenerates a third detection signal when the first and second highvoltage level detection signals are active at about the same time; anoscillation signal generator, which generates a first oscillation signalin response to the first high voltage level detection signal or thesecond high voltage level detection signal and generates a secondoscillation signal by dividing the first oscillation signal; a firsthigh voltage pumping control signal generator, which generates a firstsignal from the second oscillation signal when the third detectionsignal is generated and generates a first high voltage pumping controlsignal from the first oscillation signal in response to the first highvoltage level detection signal or the first signal; and a second highvoltage pumping control signal generator, which generates a secondsignal from an inverted second oscillation signal when the thirddetection signal is generated and generates a second high voltagepumping control signal from the first oscillation signal in response tothe second high voltage level detection signal or the second signal,wherein the control signal generator generates the at least threepumping control signals in response to the first high voltage pumpingcontrol signal and generates the at least one of the at least threepumping control signals in response to the second high voltage pumpingcontrol signal.
 4. The voltage generation circuit according to claim 3,wherein the control signal generator generates a first precharge controlsignal in response to the first one of the at least three pumpingcontrol signals, generates a second precharge control signal in responseto the first one and the second one of the at least three pumpingcontrol signals, and generates a third precharge control signal inresponse to the first one, the second one, and the third one of the atleast three pumping control signals.
 5. The voltage generation circuitaccording to claim 4, wherein the voltage generator comprises: a firstand second pumping and precharge unit, which pumps a first node and asecond node in response to the first one of the at least three pumpingcontrol signals and performs charge sharing operations between the firstnode and the boost node and between the second node and a third nodeduring the generation of the first high voltage, and precharges thefirst and second nodes in response to the first precharge controlsignal; a third pumping and precharge unit, which pumps the third nodein response to the second one of the at least three pumping controlsignals and performs a charge sharing operation between the third nodeand the boost node during the generation of the first high voltage, andprecharges the third node in response to the second precharge controlsignal; and a fourth pumping and precharge unit, which pumps the boostnode in response to the third one of the at least three pumping controlsignals and performs a charge sharing operation between the boost nodeand a first high voltage generation terminal during the generation ofthe first high voltage, pumps the boost node in response to the thirdone of the at least three pumping control signals and performs a chargesharing operation between the boost node and a second high voltagegeneration terminal during the generation of the second high voltage,and precharges the boost node in response to the third precharge controlsignal.
 6. The voltage generation circuit according to claim 5, whereinthe first and second pumping and precharge unit comprises: a firstswitch, which is connected between a power supply voltage and the firstnode and precharges the first node in response to the first prechargecontrol signal; a first capacitor, which pumps the first node inresponse to the first one of the at least three pumping control signals;a second switch, which is connected between the power supply voltage andthe second node and precharges the second node in response to the firstprecharge control signal; a second capacitor, which pumps the secondnode in response to the first one of the at least three pumping controlsignals; a third switch, which is turned on in response to the first oneof the at least three pumping control signals and allows charge to beshared by the first node and the boost node; and a fourth switch, whichis turned on in response to the first one of the at least three pumpingcontrol signals and allows charge to be shared by the second node andthe third node.
 7. The voltage generation circuit according to claim 6,wherein the third pumping and precharge unit comprises: a fifth switch,which is connected between the power supply voltage and the third nodeand is turned on in response to the second precharge control signal toprecharge the third node; a third capacitor, which pumps the third nodein response to the second one of the at least three pumping controlsignals; and a sixth switch, which is turned on in response to thesecond one of the at least three pumping control signals and allowscharge to be shared by the third node and the boost node.
 8. The voltagegeneration circuit according to claim 7, wherein the fourth pumping andprecharge unit comprises: a seventh switch, which is connected betweenthe power supply voltage and the boost node and precharges the boostnode in response to the third precharge control signal; a fourthcapacitor, which pumps the boost node in response to the third one ofthe at least three pumping control signals; an eighth switch, whichallows charge to be shared by the boost node and the first high voltagegeneration terminal in response to the third one of the at least threepumping control signals during the generation of the first high voltage;and a ninth switch, which allows charge to be shared by the boost nodeand the second high voltage generation terminal in response to the thirdone of the at least three pumping control signals during the generationof the second high voltage.
 9. The voltage generation circuit accordingto claim 4, wherein the voltage generator comprises: a first and secondpumping and precharge unit, which pumps a first node and a second nodein response to the first one of the at least three pumping controlsignals and performs charge sharing operations between the first nodeand the boost node and between the second node and a third node duringthe generation of the first high voltage, and precharges the first andsecond nodes; a third pumping and precharge unit, which pumps the thirdnode in response to the second one of the at least three pumping controlsignals and performs a charge sharing operation between the third nodeand the boost node during the generation of the first and second highvoltages, and precharges the third node; and a fourth pumping andprecharge unit, which pumps the boost node in response to the third oneof the at least three pumping control signals and performs a chargesharing operation between the boost node and a first high voltagegeneration terminal during the generation of the first high voltage,pumps the boost node in response to the third one of the at least threepumping control signals and performs a charge sharing operation betweenthe boost node and a second high voltage generation terminal during thegeneration of the second high voltage, and precharges the boost node.10. The voltage generation circuit according to claim 1, wherein thecontrol signal generator further generates a first one of the at leastfour pumping control signals in response to a level of a power supplyvoltage.
 11. The voltage generation circuit according to claim 10,wherein the control signal generator comprises: a power supply voltagelevel detector, which generates the first one of the at least fourpumping control signal in response to the level of the power supplyvoltage, receives the first one of the at least four pumping controlsignals and outputs an output signal when the power supply voltage is ata predetermined level or higher, and deactivates the first one of the atleast foul pumping control signals when the power supply voltage is at alevel lower than the predetermined level.
 12. The voltage generationcircuit according to claim 10, wherein the voltage generator comprises:a first high voltage generator, which pumps the boost node in responseto the at least four pumping control signals to generate the first highvoltage; and a second high voltage generator, which transmits chargefrom the boost node to the second high voltage generation terminal inresponse to the control signal and the second high voltage leveldetection signal to generate the second high voltage.
 13. The voltagegeneration circuit according to claim 12, wherein the control signalgenerator generates the first one, a second one, and a third one of theat least four pumping control signals, which are activated in sequenceduring the active period of the first high voltage level detectionsignal, generates a fourth one of the at least four pumping controlsignals, which is activated during the inactive period of the first highvoltage level detection signal, generates a first precharge controlsignal in response to the first one of the at least four pumping controlsignals, a second precharge control signal in response to the first oneand the second one of the at least four pumping control signals, and athird precharge control signal in response to the first one of the atleast four pumping control signals and the control signal, generates thefirst one of the at least four pumping control signals when the powersupply voltage is at a high level, and deactivates the first one of theat least foul pumping control signals when the power supply voltage isat a low level.
 14. The voltage generation circuit according to claim13, wherein the first high voltage generator comprises: a first andsecond pumping and precharge unit, which pumps a first node and a secondnode in response to the first one of the at least four pumping controlsignals and performs charge sharing operations between the first nodeand the boost node and between the second node and a third node duringthe generation of the first high voltage, and precharges the first andsecond nodes in response to the first precharge control signal; a thirdpumping and precharge unit, which pumps the third node in response tothe second one of the at least four pumping control signals and performsa charge sharing operation between the third node and the boost nodeduring the generation of the first and second high voltages andprecharges the third node in response to the second precharge controlsignal; and a fourth pumping and precharge unit, which pumps the boostnode in response to the third one of the at least four pumping controlsignals and performs a charge sharing operation between the boost nodeand a first high voltage generation terminal during the generation ofthe first high voltage, pumps the boost node in response to the thirdone of the at least four pumping control signals and performs a chargesharing operation between the boost node and the second high voltagegeneration terminal during the generation of the second high voltage,and precharges the boost node in response to the third precharge controlsignal.
 15. The voltage generation circuit according to claim 13,wherein the second high voltage generator comprises: a second highvoltage generation unit, which transmits charge from the boost node tothe second high voltage generation terminal in response to the controlsignal and the second high voltage level detection signal.
 16. Thevoltage generation circuit according to claim 14, wherein the first andsecond pumping and precharge unit comprises: a first switch, which isconnected between the power supply voltage and the first node andprecharges the first node in response to the first precharge controlsignal; a first capacitors which pumps the first node in response to thefirst one of the at least four pumping control signals; a second switch,which is connected between the power supply voltage and the second nodeand precharges the second node in response to the first prechargecontrol signal; a second capacitor, which pumps the second node inresponse to the first one of the at least four pumping control signals;a third switch, which is turned on in response to the first one of theat least four pumping control signals and allows charge to be shared bythe first node and the boost node; and a fourth switch, which is turnedon in response to the first one of the at least four pumping controlsignals and allows charge to be shared by the second node and the thirdnode.
 17. The voltage generation circuit according to claim 16, whereinthe third pumping and precharge unit comprises: a fifth switch, which isconnected between the power supply voltage and the third node and isturned on in response to the second precharge control signal toprecharge the third node; a third capacitor, which pumps the third nodein response to the second one of the at least four pumping controlsignals; and a sixth switch, which is turned on in response to thesecond one of the at least four pumping control signals and allowscharge to be shared by the third node and the boost node.
 18. Thevoltage generation circuit according to claim 17, wherein the fourthpumping and precharge unit comprises: a seventh switch, which isconnected between the power supply voltage and the boost node andprecharges the boost node in response to the third precharge controlsignal; a fourth capacitor, which pumps the boost node in response tothe third one of the at least four pumping control signals; and aneighth switch, which allows charge to be shared by the boost node andthe first high voltage generation terminal in response to the third oneof the at least foul pumping control signals during the generation ofthe first high voltage.
 19. The voltage generation circuit according toclaim 15, wherein the second high voltage generation unit comprises: aninth switch, which transmits charge from the boost node in response tothe control signal; and a tenth switch, which transmits chargetransmitted from the ninth switch to the second high voltage generationterminal in response to the second high voltage level detection signal.20. The voltage generation circuit according to claim 19, wherein thesecond high voltage generation unit further comprises: an eleventhswitch, which transmits charge transmitted to the second high voltagegeneration terminal to a power supply voltage generation terminal whenthe second high voltage level detection signal is inactive.